US1792200A - Dental cement and process of making the same - Google Patents

Description

Patented Feb. 10, 1931 Patent? cit-t cs IQBGEN ERNST. TEQI LSEN, Q JEBL E- 1 L JYLN JERSEY DENTAL CEMENT AND PRQCES'SOE--M-AKI1TG TH life-Drawing This. application; is. a continuation in part of my; corpendingappl tion, Ser al: N 123 012, filed, in, the. United; States Eatent Office on- 01: about July 16, L926, and, entitled 5 Improvements in dentaL cements and; processesof making the Sa-m6- This. invention relates to, a new dental: cement. and the process of making the same. Ehere are twoiypes; of; cement generally em;

1 ployed: in dental? workone is these-called Zinc oxide cement and the other, is the socalled silicate cement.

Zinc oxide cements are preparedby admixingzim idew h-b smu hi xide,.,niagnesi 1 oxide, etc. The s l catecemen cons s of alumina,lime,silica and fiuorine, etc; Elnorine may or maynot be present and is not essential.

lath pr ces fi man -factnr o zincnxid 2 ement it, is brought to, high te -npemture,

but not-suificientto se h ame; It s m rely concentrated. The product isthenground and passed'through. fine-sieves, cloth, etc, In the process of making the silicate cements,

the cement is brought to complete fusion and is then. po int m ld in imi a to. glass. The resultingproduct; is; pulverized, sieved, molded, etc.

In order to. produce a plastic mass, from 3 these, which. can be worked; and which will harden, it is necessary to mix the powder containing basic elements with-the proper proportion; of: phosphoric acid: It isunnecessary togo into the various methods of preparing the phosphoric acid asga binder for these, cements, except to. state that the ac d -r re mixe w t celt aini mo ifie s,- z nc carbon te a en m-pleiandhs te to o temperature to drive off the carbon dioxide.

lit-is then diluted with watertoltegulate the et ing ime; V

A amou t. f diflicu ta s experienced n t e use f; ental he nrpner P p' g 5 he phq phatic ac d-l Q 1- i er lythefmi uiecf esic;elem nts qm on h mat-list in; .9 2 1 Rendertlie-cemsnt i to h use he enti W llteke a suitab e e-c n Q e P d o e cmbinewi hthe s i ne t h Application filed September 20, 19218.v Serial No. 307,345;

hardened mass,willhavensatisfactory proper- 6P 7 ties n y t ch moun phospho c acid is used.i as is required to combine with: the bas onst tuents Pr s n Usuallyv an; excess of phosphoric acid is used, The free. acid remaini-n'g iiritates the puips of the teeth,cau sing-paiii, shock to the pulp a t enlo s Qf hcp lp- The objectof this invention is toeliminate this difliculty by accurately proportioning the amount of acid requiredzto combine thoroughly with agivencement by incorporating the required" acidwith the dry powder in the proc s t manu a tur fth m n and preparing same for sale in such a nauner so that allthat is requined' of; the user is to mix 3 water with the powder, apply this mixture to the tooth cavity, and thecement willsetin x ly the ame mann s i dina y ment powder had been used with phosphoric acid, as a result of which irritation and-pain or. harinto the tooth pulp are avoided to. a great extent or entirely. The phosphoric acid in the present invention is mixed at the manufacturing plant and is allowed to par tially combine with the basic elements,- and this is, preferably done without the. exte-i na application of heat.

The strengtho-f the phosphoric acidused may be varied within certain limits, and lw i ni sc sw lli s heprefe te lst cnst wi l som timesbe afi ctediby xisting dndiipns and ill lv hetewit r EQr. example. aq scQmnliis iglsst aefiflatl tn lE'z-Qjagn- 13? and. be sed advant ss s y with. ligatecement l -n 1 th, am an: id ementswh l hey m y be y f y -fo my purpose with other zinc; oxide cements whei'e the lower limit of: I I 0is 1 gHg0 to- IBEQE. Again, the temperature of calcination off the zincoxide in thepreparation thereof frequently affects the strength of the phosphoric acid which is to be preferred, as well as the range of strengths which may be used to advantage. Furthermore copper chloride or iodide, or silver salts, are sometimes added to the cements as a germicide, and such additions may affect the strengths of the phosphoric acid which is to be preferred, and it may even have an efi'ect on the range of useful strengths. Other conditions may have a like eflect. It is therefore impossible to state exactly for all cements the best strength of the phosphoric acid to be used therewith or the limits within which it maybe varied.

I can state, however, as a general rule that the ratio of H 0 to P 0 should not be less than 2H O to 11 0 in the case of phosphoric acid used with silicate cements, and l fl H O to 11 0 for acid used with zinc oxide cements; although as already stated this ratio should not be less than 2 to 1 even for some zinc oxide cements. Less than 1 I-I O to 1P O is usually ineffective for dental cements, but this low limit of H 0 in the acid is under certain conditions sometimes outside of the advantageous limits. As stated above, various conditions will cause variations in the strengths of the phosphoric acid which it is best to use, as well as of the limits of strengths which may be used. I generally prefer to use acid of a strength of 3H O to 1P O that is orthophosphoric acid, H PO The composition of ordinary phosphoric acid of commerce is usually P O 4I-I O and it is necessary to add metaphosphoric acid (1 0 -11 0) to bring the H 0 and P 0 into the proper proportions. Although the proportion P O 3I-I O is preferred, it may vary between, say, P O 3 H O and P 0 QH O, or even P O 1 H O as above stated. Too much water is to be avoided, sinceitwould cause premature hardening of the cement.

The following are examples of some silicate cements:

1 II Na SiF 142 142 Cali 2O 20 Al O .xH O 158 158 SiO 102 114 parts of the cement to50 parts of phosphoric acid.

Zinc oxide cements, for example, cements comprising parts of zinc oxide and 10 parts of magnesium oxide or corresponding quantities of magnesium carbonate or/and silicofluoride would require relatively more phosphoric acid, due to greater basicity. A suitable mixture could be formed from 150 parts of zinc oxide cement and parts of phosphoric acid, but the amount of phos phoric acid may be varied between 100 and 150 parts.

The powder and the phosphoric acid are mixed together at room temperature, the reaction between them generating suflicient heat, under ordinary working conditions to heat the mass to about between about 100 and 180 F. or about 30 to 70 C., which is sufficient to cause removal of the excess water present; and allowing the mass to stand until cool will enerally result in a dry mass which is then to be comminuted or powdered.

Apparently the phosphoric acid is present therein in some combined form and this seems to become cementitiously active on the addition of water. While this seems to be the case, yet I do not intend to restrict my invention'to any theory; but aside from any theory, the dry powder when mixed with water as above described becomes cementitious and sets.

The resulting powder is packaged for sale. It is ready for use and it is necessary only to add the desired amount of water to produce a desirable plastic mass ready for use and which upon standing will readily harden. The thinner it is desired to make this cement, for example cementing for crown and bridge work to teeth,the more water will be added. Less water will be added when a thick plastic mass is desired, as for filling teeth.

The specific proportions given above are merely illustrative and this invention is of broad application to all dental cements of the character above described. The composition both in respect to constituents and proportions may be widely varied.

Having described my invention, what I now claim is:

1. The herein-described composition of matter in dry powder form suitable for use as a dental cement by the addition thereto of water alone, said composition consisting of approximately parts by weight of a silicate cement and from 40 to 60 parts by weight of pure orthophosphoric acid or the equivalent of said acid in P 0 radical, said ingredients being mixed'together at a temperature sufficiently low to retain the mixture in an unstable condition capable of subsequently re acting with the added water to form aplastic mass capable of hardening. p

2. The herein-described composition of matter in dry powder form suitable for use as a dental cement by the addition thereto of water alone, said composition consisting of approximately partsby weight of a basic metaloxide cement and from 100" to 150 parts by weight of a phosphoric acid containing the P radical in combination with from 1 to 2 molecules of combined Water, said ingredients being mixed together at a 5 temperature sufficiently low to retain the mixture in an unstable condition capable of subsequently reacting with the added Water to form a plastic mass capable of hardening.

J ORGEN ERNST THOMSEN.